World production of rhodium (from the Greek rhodon, "rose") is about 10 tons. While the metal itself has few applications, it is an important alloying agent used as a hardener for platinum and palladium. Rhodium was discovered in 1803 by William Hyde Wollaston who named it for the rose-red color of its salts.
Rhodium is part of the the Platinum Group Metals (PGM) whic is located in the 5th and 6th rows of the transition metal section of the periodic table and includes Ruthenium, Rhodium, Palladium, Osmium, Iridium, and Platinum. Common characteristics include resistance to wear, oxidation, and corrosion, high melting points, and oxidation states of +2 to +4. They are generally non-toxic. It shares the properties of these metals: high corrosion resistance, hardness and ductility. It is the rarest of the group, only occurring to the extent of about 1 part per 200 million in the earth's crust.